1. Field of the Invention
This invention relates generally to methods and systems for determining the impact point and damage propagation in a detection surface and, more particularly, to a method for determination of multiple shrapnel hits on a ballistic target threat.
2. Background Art
The Department of Defense (DOD) of the U.S. government has developed anti missile technology to protect the United States and allied interests against attack by different threat missiles. Threats may be ballistic in nature. That is, they are carried outside of the atmosphere by a rocket to extend the range of the weapon and subsequently re-enter the atmosphere and are guided to their intended target by external commands or internal guidance logic. Other threats may fly close to the earth to avoid radar and other short range defense systems via speed and maneuverability at “map of the earth” altitudes.
Defensive missiles have been designed as “hit-to-kill” weapons where a kinetic warhead (KW) on the killer (defensive) missile acquires the target threat and is guided to that target via external inputs as well as internal sensors and logic. This technique is adequate for many types of threat missiles. However, new threats may require a different approach to the “end game” kill scenario. This new technology is referred to as a “shrapnel kill” weapon. It is to missiles as a shot gun is to a goose hunter. The killing mechanism is not a simple one-piece kinetic warhead (KW); but, instead, it explodes into many shrapnel fragments when sensors indicate it is close enough to the target. The shrapnel fragments maintain the forward velocity of the killer missile as well as the additive acceleration and final velocity provided by the fragmenting explosive. This process is similar to a WW2 technology for hand grenades.
“Hit to Kill” weapons have been judged for their accuracy by lethality assessment systems that are installed and flown within the payloads of the “threat representative” target missiles. Historically, most impact and lethality assessment systems and methods for determining the impact point and damage propagation in a detection surface, such as ballistic missile intercepts, micrometeoroids and orbital debris (MMOD) or other shock events typically utilize wire or optical grids that form a mesh over the surface of the target missile. These grid systems report the initial hit point by monitoring the X/Y matrix of the grid and accurately determine the timing and sequence of broken conduction paths. This data is compiled and transmitted off of the target missile very quickly so as to avoid inevitable destruction of the target by the killer missile.
The conventional lethality assessment capability is dependent upon the X/Y grids created by the optical or wire conductors. This technique works well for “Hit to Kill” weapons since there will only be one impact. However, in a “Shrapnel Kill” environment, each target missile may take many hits from the shrapnel generated from the explosion of the warhead from the kill vehicle. Conventional wire/optical grids ignore a wire or optical path when it is broken rendering it useless, thus, it is impossible utilizing current lethality assessment methods to accurately record multiple random hits from shrapnel on a grid because once a path is broken by one hit, future hits, involving that conductive path, are not detected and, as a result, would create incorrect tabulation of the multiple hits from the shrapnel kill vehicle. Thus, there is a need for a new lethality assessment technology that would be useful in shrapnel kill systems
Invocon, Inc., of Conroe, Tex. has developed and patented several lethality assessment systems that employ a “wireless hit grid” that utilizes impact energy to locate the exact point of initial contact and damage propagation in the detection surface. The following are some examples.
Heermann et al, U.S. Pat. No. 8,279,425, assigned to Invocon, Inc., commonly owned with the present application, and incorporated herein by reference in its entirety, discloses a frequency domain reflectometry (FDR) lethality assessment method and system for determining impact point and damage propagation in detection surface that utilizes frequency domain reflectometry (FDR) to determine impact point and damage propagation faults in the detection surface. The detection surface has a conductive layer capable of propagating radio frequency (RF) signals. At least one signal transmit/receive port on the detection surface injects a radio frequency (RF) interrogation signal into the detection surface and at least two signal receive-only ports on the detection surface spaced a distance apart from each other and from the signal transmit/receive port receive reflected radio frequency (RF) signals of the interrogation signal. A frequency domain reflectometry measurement system coupled with the transmit/receive port and signal receive-only ports measures frequency responses of the ports compared to predetermined baseline measurements and determines the precise location of an impact point and damage propagation fault in the detection surface by triangulation.
Kiefer et al, U.S. Pat. No. 8,307,694, assigned to Invocon, Inc., commonly owned with the present application, and incorporated herein by reference in its entirety, discloses a hypervelocity impact detection method and system for determining the precise impact location in a detection surface, of impacts such as ballistic missile intercepts, micrometeoroids and orbital debris (MMOD) or other shock events, that utilizes a gridless detection surface capable of propagating radio frequency (RF) impact detection signals responsive to receiving hypervelocity impacts from objects, and multiple sensors on the detection surface that directly measure radio frequency RF emissions generated by the hypervelocity impacts on the surface, and a time of arrival (TOA) position measurement technique for determining the precise impact location in the detection surface.
Kiefer et al, U.S. Pat. No. 8,316,690, assigned to Invocon, Inc., commonly owned with the present application, and incorporated herein by reference in its entirety, discloses a hypervelocity impact and time of arrival detection method and system for detecting hypervelocity impacts on a detection surface utilizing multiple sensors that directly measure electrical pulse radio frequency (RF) emissions generated by hypervelocity impacts on the detection surface and time of arrival (TOA) position measurements for determining the precise impact location on the detection surface. The detection surface material is compressed differentially in such a way that the inherent equalization of the compressed electron density in one area of the impact is directed to the uncompressed area of the material causing an electrical current that flows until the redistribution of the electrical charge has been completed and the rapid redistribution of charge and inherent current that results emits the radio frequency pulse that is induced into the detection surface.